Altimeter Setting being broadcasted.

[crxcte]

Ever tested your altimeter setting at an airport?  Roll over the approach end of the runway look at the approach plate surveyed height and compare your altimeter setting being broadcast.  If your altimeter on the panel is 4' off the ground you should be 4' higher than the approach plate height.

[jetdriven]

Within  +/- 75 feet is legal.  The static port is on the rear fuselage.

[Hank]

Yep, and neither my altimeter window nor G327 transponder show altitude in single-foot increments. The altimeter has a "/" every 20', and the transponder moves in 100' increments [at least that's all I've ever noticed it sending, even when the Mode C was erratic and reporting anything from -10,000' to 27,000'].

[crxcte]

Altimeter cert requirements:

The tolerances, at the lower altitudes, are: (Appendix E 14 CFR 43)

0 ±20'
500 ±20'
1000 ±20'
1500 ±25'
2000 ±30'
3000 ±30
4000 ±35
6000 ±40
8000 ±60

FAA Altimeter Requirements are +/-20' or .02 inch Order 6560.13C.

Where is +/-75' variation listed?

[jetdriven]

AIM 7-2-3.  You cna calibrate an altimeter at a instrument shop but you cannot account for temperature and pressure variables.  So the AIM suggests 75 feet as a reference to suspect it as being innacurate. 

http://www.faa.gov/air_traffic/publications/atpubs/aim/Chap7/aim0702.html

""3. Note the variation between the known field elevation and the altimeter indication. If this variation is in the order of plus or minus 75 feet, the accuracy of the altimeter is questionable and the problem should be referred to an appropriately rated repair station for evaluation and possible correction.""

[crxcte]

Quote: jetdriven

AIM 7-2-3.  You cna calibrate an altimeter at a instrument shop but you cannot account for temperature and pressure variables.  So the AIM suggests 75 feet as a reference to suspect it as being innacurate. 

http://www.faa.gov/air_traffic/publications/atpubs/aim/Chap7/aim0702.html

""3. Note the variation between the known field elevation and the altimeter indication. If this variation is in the order of plus or minus 75 feet, the accuracy of the altimeter is questionable and the problem should be referred to an appropriately rated repair station for evaluation and possible correction.""